# Copyright 2025 the LlamaFactory team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from typing import Optional

from torch.distributed.device_mesh import DeviceMesh


class DeviceMeshManager:
    """Device mesh manager."""

    _instance: Optional["DeviceMeshManager"] = None
    _initialized: bool = False

    def __new__(cls) -> "DeviceMeshManager":
        if cls._instance is None:
            cls._instance = super().__new__(cls)
        return cls._instance

    def __init__(self) -> None:
        if self._initialized:
            return

        self.device_mesh: Optional[DeviceMesh] = None
        self._initialized = True
